Means for transmitting torque in mechanical devices have always been of great importance. Often, several devices, e.g., axles, must use connectors to transmit torque from one axle to the other or to any third body. Connection means for transmitting torque include gearing, slot and key connections, rigid fastenable couplings, clutch or friction couplings, etc.
Spline gears are an important torque transferring device. Large torque components may be transferred via a spline gear connection. In addition, spline gear connections provide the capability of disengaging or engaging the torque transmission at the desire of the operator.
The performance of spline gears is dependent upon the precision with which they are prepared. The performance of precision spline gears can be hindered by the presence of excessive friction between the mated spline parts. Interchangeability between lot sizes of production spline parts can be affected by spline tolerances. Undesirable friction may be the result of surface irregularities, burrs, galling, poor or inadequate machining techniques.
Methods of finishing the surfaces of spline gears to a precision necessary for their smooth and dependable operation are generally limited to a polishing type procedure known as lapping. Hand lapping is the traditional method applied. Hand lapping is accomplished by mating the female portion with the male portion of the gear, or mating either gear with what is known as a tool which, in reality, is nothing more than the opposite embodiment of the gear. Using a very fine grinding or polishing compound, hand lapping is accomplished by reciprocally sliding the first piece against the second piece, or by sliding the gear in and out of the tool piece.
Hand lapping spline parts removes friction, thereby increasing the performance. However, hand lapping operations are inconsistent, monotonous and extremely time-consuming.